Corn plant named Tripsacorn

ABSTRACT

A new and distinct corn plant that is the product of a cross between Tripsacum dactyloides and Zea diploperennis, a diploid perennial teosinte. This plant is fertile, has been proven to be cross compatible with Zea mays L. and offers an avenue to expand the gene pool for commercial corn varieties. The instant plant is perennial, offers outstanding drought and heat tolerance, has survived temperatures of 0 degrees Fahrenheit, and offers enhanced pest resistance for importation into corn through improvement breeding programs.

BACKGROUND OF THE NEW PLANT

Two wild grasses, Zea diploperennis and Tripsacum dactyloides have beencrossed to produce a novel hybrid that may improve corn by impartingbeneficial characteristics including pest resistance and droughttolerance. Zea diploperennis (hereafter referred to as diploperennis), adiploid perennial teosinte and previously unknown wild relative ofmaize, was discovered on the verge of extinction in the mountains ofJalisco, Mexico in 1979. Diploperennis is in the same genus as maize,has the same chromosome number (n=10), and hybridizes easily with it.Tripsacum, a more distant relative of corn with a different chromosomenumber (n=18), has been crossed with maize by artificial means but hasnot been known to cross with teosinte. Many investigators believe thatTripsacum played a prominent role in the origin and evolution of maize,and that it has significant potential for improving corn by expandingits genetic diversity.

In 1984, crosses were made to diploperennis using Tripsacum pollen andU.S. Plant Pat. No. 6,906, was issued Jul. 4, 1989 on the hybrid fromthat cross. In Apr., 1985, the reciprocal cross to Tripsacum was madeusing diploperennis pollen. The plant germinated from the hybrid seed[labeled (Trip X 3-3)] developed normally, was fully fertile andproduces viable fruits. This plant is referred to as Tripsacorn. Thechromosome number determined from root tip counts is 2n=20 or 2n=18.There is evidence in late prophase and metaphase for chromosome fusion.Some chromosomes are linked end to end in a chain formation and othershave the trisomic y-shaped configuration. Although the chromosome numberis unexpected, it has been reasonably ascertained that the genotype forthis plant is normal and stable.

Perennial plants have been propagated by means of cuttings and rhizomedivisions. In field tests, they have produced new growth followingwinter temperatures of 0° F. and have survived summer drought for sixweeks.

In preliminary field trials of backcrosses to a commercial corn line,drought tolerance and enhanced pest resistance were observed in the F₁generation. Germination of seed from these crosses was 100%. The plantswere fully fertile and there was no loss in productivity. Tripsacornevidently provides a natural bridge for introducing Tripsacum germ plasminto corn, thereby establishing a link between these wild grasses andmodern corn that may be beneficial in corn improvement breedingprograms. The results of crossing Tripsacorn, labeled (Trip X 3-3), tocorn were distinctly different from the results of crossing the patentedplant Sun Dance, labeled (3-7X Trip), to corn. When Sun Dance wascrossed to corn, the F₁ plants were depauperate in growth and highlysusceptible to insects and disease; whereas plants grown from TripsacornX corn were sturdy, more tolerant of the drought conditions during thesummer of 1988, were resistant to the plant pests that plagued the cornthat season, were stocky with strong stalks and more extensive rootsystems, were fertile and produced ears weights equal to the corncontrols.

Unique propagation of Tripsacorn through successive generations by meansof cuttings has demonstrated that the new plant has not only retainedthe continuous and abundant production capability, but also that itsdistinguishing characteristics hold true from generation to generationand appear to be firmly fixed. Propagation has taken place in Tennessee,North Carolina, and Mississippi.

DESCRIPTION OF ILLUSTRATIONS

This new corn plant is illustrated by the accompanying photographs,which show:

(1) a plant grown outdoors showing the characteristic habit of manyculms growing from the base, each of which produce a separate tassel atthe apex;

(2) the long, narrow leaf with distinctive white midrib;

(3) an individual culm showing distinctive red coloration and earsemerging from leaf sheaths at the nodes;

(4) a close-up of a three-branched tassel with emerged anthers sheddingpollen;

(5) a close-up of the two variations of single-rowed female spikes thatare produced, one in which the male flowers are subtended by the femaleinflorescence and one that is solely a single-rowed female spike;

(6) a side view of a segment of the alternate type of inflorescence thatforms a four-rowed cob consisting of paired kernels partially enclosedby hard glumes;

(7) two other side views of the cob showing the distinctive interspacingbetween segments with a separate section of the rachis segment showingthe ball and socket abscission characteristic of the Tripsacum parent,cupule, and a removed kernel;

(8) an autoradiograph showing the banding patterns of Tripsacorn (Trp X3-3), Sun Dance (3-7 Trip), a diploperennis parent (3-7), the Tripsacumparent (Trip) and two corn controls (CM37 and T232), when the DNA wasdigested by BamH1 and probed with BNL 17.07, a nuclear probe to the longarm of maize chromosome 10;

(9) an autoradiograph of DNA from the same plants digested with Bam H1and Hind III that reveals cytoplasmic differences as evidenced by thedifferent banding patterns of (Trip x 3-3) and (3-7 X Trip) when probedwith a maize mitochondrial ATPase gene.

THE PLANT

Origin: Seedling.

Parentage:

Seed parent.--Tripsacum dactyloides. Source: Plant established atIndiana University, Bloomington, Ind., originally collected from SantaClaus, Spencer County, Ind., 1949-54.

Pollen parent.--Zea diploperennis. Source: Upper las Joyas, Sierra deManantlan, Jalisco, Mexico, Iltis, Nee & Guzman Acc. #1250, Jan. 1979.

Classification:

Botanic.--Zea indiana (proposed).

Habit: Essentially erect; as many as 35 primary culms, usual numberabout 15.

Duration:

Perennial.--Sends out shoots from rhizomes. Plant will freeze at wintertemperatures below 28° F., but new growth is produced in spring afterwinter temperatures of 0° F.

Culm:

Height.--Up to two meters; slender, simple with occasional branchingfrom the nodes of the culm; glabrous; oval in cross section; diameter1-12 cm.

Nodes.--Glabrous, aerial roots develop at nodes along entire culm.

Sheath.--Tightly closed enwrapping the culm, margins not united;glabrous; turns rose red (Pantone #18-1852) when exposed to sun,otherwise green; rose red (Pantone #18-1852, ciliate auricles at summitmargins.

Ligule.--Present on adaxial side of leaf at junction of blade andsheath; length: 4 mm; membranaceous, irregular edge.

Leaf blade: Alternate; distichous; sheathing base; parallel veined;narrowly linear, flat, thin.

Length.--47-56 cm. Width: 1.5-5.0 cm.

Entire margin.--Rose red (Pantone #18-1852), serrulate.

Midrib.--White (Pantone #12-5202).

Adaxial surface.--Sparsely hirsute.

Abaxial surface.--Glabrous except sparsely hirsute along midrib.

Prominent parallel veins.--5 per 1 cm width.

INFLORESCENCE

Blooming period: Twice annually in the greenhouse for approximately onemonth beginning in late April and late October in Tennessee, NorthCarolina and Mississippi.

Monoecious: Separate male and female flowers on the same plant;variable.

Staminate flowers: May be of two types: one inflorescence type borne aspaired spikelets on a slender rachis forming 3-7 racemes arranged in apanicle, the "tassel", at the summit of the culm. Alternatively,staminate spikelets may be borne on a single spike above the pistillateflowers.

Length.--6-12 cm.

Axis.--Stiff, continuous, ascending.

Spikelet: Two-flowered, one sessile, one pediceled; laterally compressedawnless, attenuate with red (Pantone #19-1860) tip and red (Pantone#19-1860) band at base; Length: 11 mm; Width: 3 mm. In pairs on one sideof a persistent central axis.

Pedicel length.--3 mm.

Glumes.--Outer glume: cartilaginous, tapering to an acute tip, ciliate,flat, several nerved, margins involute, fimbriate. Inner glume:chartaceous.

Pistillate flowers: Borne in leaf axils; spikelets distichouslyarranged; variable.

Styles.--Pilose with distinct bifurcated tips.

Color.--Ranges from pastel parchment (Pantone #11-0603) to light lilac(Pantone #12-2903) to rose red (Pantone #18-1852).

Length.--100 mm.

One type of pistillate flower consists of a single rowed spike of 4 to 6triangular caryopses in hard, shell-like fruitcases enclosed in a singleleaf sheath; caryopses disarticulate upon maturity. Length: 7.5 mm;Width: 5 mm. Colors range from solid to variegated combinations of thefollowing: White (Pantone #11-0602), gray (Pantone #16-1107), tobaccobrown (Pantone #17-1327), brown (Pantone #19-1121), dark brown (Pantone#19-1020). Alternatively, spikelets paired and partially enclosed instiff, brown speckled glumes; caryopses rounded and imbricate; Spikesenclosed in single or multiple leaf sheaths. Caryopses do notdisarticulate upon maturity; Length: 5 mm; Width: 5 mm. Color variegatedcombinations of the following: dark brown (Pantone #19-1217), brown(Pantone #18-1154), beige (Pantone 15-1225), light beige (Pantone#13-1018).

Fruit.--Five to ten ears per culm per blooming period; flowers areproduced twice a year under greenhouse conditions; some plants mayproduce approximately 150 ears twice annually.

Maturity.--45 days following fertilization.

A. Ear (husked ear data unless stated otherwise):

Length.--About 43 mm.

Midpoint diameter.--About 6.7 mm.

Weight.--0.5 gm.

Kernel rows.--2 (rarely 3-4).

Silk color (exposed at silking stage).--light lilac (Pantone #12-2903)to rose red (Pantone #18-1852).

Husked color.--Cob kernels are embedded in the rachis segments, some ofwhich disarticulate upon maturity. These segments are brownish gray andare the hard, boney fruitcase enclosing the kernels.

Kernel color.--beige (Pantone #14-1122) shading to golden beige (Pantone#16-1336).

Husked extension (harvest stage).--About 1 cm.

Shank.--About 6.5 cm.

Taper.--Slight.

Position in dry husk stage.--Upright.

Drying time (unhusked ear).--About 2-3 days.

B. Kernel (dried):

Type I.--Angular caryopses in hard, shell-like fruitcases, disarticulateupon maturity; Size (from midpoint): Length about 0.8 mm, Width about0.5 mm, Thickness about 0.4 mm. Shape: Trapezoidal. Colors range fromsolid to variegated combinations of the following: white (Pantone#11-0602), gray (Pantone #16-1107), tobacco brown (Pantone #17-1327),brown (Pantone #19-1121), dark brown (Pantone #19-1020). Weight 20 seeds(unsized samples): 1.3 gm.

Type II.--Paired caryopses partially enclosed in endurated glumesforming a cob, upon maturity do not disarticulate: Size (from midpoint):Length about 3.9 mm, Width about 2.8 mm, Thickness about 2.7 mm. Shapegrade (% round): 100% round (tip pointed). Pericarp color: beige(Pantone #14-1122) shading to golden beige (Pantone #16-1336). Aleuronecolor: Clear. Endosperm color: White (Pantone #11-0601). Endosperm type:Pop. Weight 20 seeds (unsized sapmles): About 0.4 gm.

C. Cob:

Diameter at midpoint.--5.3 to 8.7 mm.

Strength.--Variable.

Color.--Smoke (Pantone #12-0704).

Alicole.--Length: About 6.6 mm. External width: 7.0 mm. Internal width:5.0 mm. External length: 5.5 mm. Internal length: 5.0 mm. Overalllength: 6.4 mm. Thickness: About 4.5 mm. Depth: 2.9 mm.

Cupule.--Overhang: About 0.6 mm. Left wing width:--1.0 mm. Right wingwidth: 1.3 mm. Wing height: 4.1 mm. Lower glume length: 5.9 mm. Lowerglume angle: About 20°. Lower gllume width: About 3.0 mm. Glume cushionwidth: 5.4 mm. Glume cushion height: 1.8 mm. Sessile thickness: 0.3 mm.Cupule pubescence: sparse, short hairs. Color: Buff (Pantone #13-1024).

COMPARATIVE PARENTAL CHARACTERISTICS

Leaf blade: Zea diploperennis round in cross section; diam. 1 cm.Tripsacum dactyloides oval in cross section; diam. 1.3 cm.

Leaf blade: Z. diploperennis. Width 1-2 cm; margins pink serrulate frommidsection of blade to tip; adaxial surface: sparsely hirsute; prominentveins: 6 per 1 cm width. T. dactyloides. Width: 1 cm; margins whiteserrulate along entire blade; Adaxial surface: hirsute; prominent veins:12 per 1 cm.

Blooming period: Z. diploperennis twice a year in the greenhouse, end ofMarch and end of September for about a month. T. dactyloidescontinuously from May to October.

Stamiante flowers: Z. diploperennis borne in tassel at summit of culm.T. dactyloides staminate flowers borne above pistillate flowers insingle spike.

Pistillate flowers: Z. diploperennis caryopsis triangular-trapezoidal inhard bondy fruitcases; Length: 8 mm; Width: 4-5 mm; Color: black(Pantone #19-030), dark brown (Pantone #19-1020) or mottled black-brown.T. dactyloides caryopsis trapezoidal in hard, bony fruitcase; Length:6-10 mm; Width: 6 mm. Color: pale brown (Pantone #17-1137) or buff(Pantone #13-1024).

Color reference: Leatrice Eiseman and Lawrence Herbert, The Pantone Bookof Color. Harry N. Abrams, Inc., Publishers, New York, 1990.

COMPARISON TO SUN DANCE, U.S. PLANT PAT. NO. 6,906

Although this plant appears quite similar to Sun Dance phenotypically,it is distinct in some traits. It is resistant to aphids and whiteflies; Sun Dance is not. It has a glossy leaf surface evidenced by asilvery sheen when held under water. Sun Dance does not have such glossyfoliage. Tripsacorn is also demonstrated by molecular assay to bedistinct from Sun Dance in its nuclear and cytoplasmic DNA as revealedby banding differences to southern blots using nuclear and mitochondrialDNA probes.

I claim:
 1. A new and distinct variety of corn plant, substantially asherein shown and described, characterized by its profuse production offruit, multiple types of inflorescence, bifurcated style, perennialhabit, drought tolerance and pest resistance.